The present invention relates to a method and a device for controlling operational sequences, particularly in a vehicle, at least one sensor being connected to at least one control unit for controlling the operational sequences, and sensor information being transmitted to the control unit.
Today, vehicle sensors, particularly the sensors in the exhaust-gas branch such as lambda sensors and hot-film air-mass meters, are generally connected in a conventional manner via a cable harness to a control unit, particularly the engine control unit. Appropriate hardware lines are available for the signals and voltage supplies.
However, smart sensor technology having bus capability is discussed in the article by Heintz and Zabler xe2x80x9cEinsatzmxc3x6glichkeiten und Zukunftschancen intelligenter Sensoren im Kraftfahrzeugxe2x80x9d (xe2x80x9cUse Possibilities and Future Chances of Intelligent Sensors in the Motor Vehiclexe2x80x9d) from the BOSCH Technical Reports 1990, issue 52, pp. 30 through 41, which corresponds to the German version of the lecture at the SAE Conference in Detroit in March 1989. In the vehicle concepts in that context, multiple measurements of quantities are carried out, which are needed by electronic systems in the motor vehicle. By adding electronic components, the corresponding sensors are provided with signal preprocessing and given bus capability, i.e. are made multiply utilizable. A bus concept thereby results in which intelligent sensors having electronics locally are connected to at least one control unit.
In order to couple sensors to a control unit with the aid of a bus system, particularly a CAN bus system, diverse time conditions are observed, particularly in the case of real-time-critical applications, for example, for sensors of the exhaust branch in connection with the engine control unit. Such an optimal or optimized synchronization of the sensor suite with the control device, i.e. the control unit, is the subject matter of the present invention.
The present invention is based on a method for controlling operational sequences, particularly in a vehicle, at least one sensor having a connection unit being connected via a bus system to at least one control unit for controlling the operational sequences, the control unit likewise having a connection unit, and sensor information being transmitted to the control unit, the control unit reading in and/or processing the sensor information at specifiable synchronization points, the control unit advantageously transmitting a trigger signal via the bus system to the sensor in such a way with an allowance that the sensor information is available at the synchronization point for the control unit in a manner that it is able to be read in and/or processed. Consequently, as a basic prerequisite for the description of a sensor bus, particularly for the exhaust branch, the sensors and control unit are expediently synchronized such that the sensor information is transmitted to the control unit, i.e. is present at the control unit, just when the control unit should also read in and/or process the control information. By using a trigger signal via the bus system, the cabling expenditure, reduced by the sensor connection, can be reduced even further, since it is advantageously possible to dispense with an additional hardware trigger line, bringing with it great potential for cost savings.
If the sensor expediently contains a processing unit which preprocesses the sensor information, the allowance is advantageously predefined and/or adapted according to the time for preprocessing the sensor information.
The allowance, according to the present invention, of the trigger signal with respect to the synchronization point can advantageously ensure high topicality of the sensor information.
In one advantageous refinement, the allowance can be predefined and/or adapted in a variable manner, as a function of at least one performance quantity stemming from at least one operational sequence, in particular as a function of the engine speed. Thus, the dynamic influence of specific performance quantities assignable to operational sequences, particularly the engine speed, is advantageously taken into consideration.
The allowance is advantageously predefined and/or adapted as a function of at least one of the following influences:
a transmission time of the trigger signal from the processing unit of the control unit to its connection unit with the bus system;
a transmission time or waiting time up to the termination of a bus message already transmitted via the bus system, until the trigger signal or the sensor information can be transmitted;
a transmission time of the trigger signal itself via the bus system;
a transmission time of the trigger signal from the connection unit of the sensor to the processing unit of the sensor;
a processing time until the processing unit in the sensor has finished processing the sensor information and/or
a transmission time of the sensor information from the sensor to the control unit, which includes the transmission time from the processing unit to the connection unit of the sensor and the transmission time from the connection unit of the sensor via the bus system to the connection unit of the control unit, as well as the transmission time from the connection unit of the control unit to the processing unit of the control unit.
The allowance is advantageously determined in the form of a time quantity as a time allowance, or in one advantageous refinement in the form of an angle quantity as an angle allowance. In this context, a time allowance and an angle allowance, respectively, can be converted into one another. This conversion of the time allowance into an angle allowance, taking into account the angular velocity, has the advantage that the performance quantity, particularly the engine speed, is calculated only at the synchronization point, since the instantaneous angle, especially the crankshaft angle, is available, for example, at an engine control unit, and therefore the trigger signal can be transmitted as a function of this angle information. Due to the restriction of the calculation of the performance quantity, particularly the engine speed, to the synchronization points which is thereby possible, considerable computing power and computing time can be saved in the control unit.
To ensure the topicality of the software trigger signal, a high priority, particularly the highest priority within the framework of transmission via the bus system is assigned to the software trigger signal. The sensor information is also advantageously transmitted with high priority.
In one advantageous refinement, the sensor information and the trigger signal are transmitted in a line-less manner between the connection unit of the at least one sensor and the connection unit of the control unit; in this advantageous embodiment, the connection units are designed as transmitter/receiver units of a line-less bus system, particularly a radio bus system. This advantageously permits even greater savings on line links.